With vehicle-makers taking a greater interest in using recycled materials, Ruari McCallion investigates the processes and challenges involved
Ford Motor Company’s new F-150 trucks have been the target of some criticism for their size, weight and thirst, but according to the OEM the model will feature unprecedented levels of environmentally-friendly materials.
F-150s will use rice hulls instead of talc reinforcement in the plastic parts of electrical harnesses; the equivalent of about ten pairs of jeans will supply the carpet insulation or sound absorber; a thermoplastic material made from recycled tyres and consumer-recycled polypropylene (PP) will be used to make shields and some underbody covers; and a lightweight fibre derived from recycled PET bottles will comprise the truck’s wheel liners and shields. The current Focus model uses the product of 22 PET bottles in the fabric of each seat.
However, fabrics made of recycled material are now quite widespread and these applications are not stretching the boundaries of recycling. The more challenging applications are under the hood. Here, Ford is using material from recycled carpets for cylinder head covers in the F-150 and a number of other vehicles.
But even this pales beside a vehicle like the Nissan Leaf, which features recycled materials in almost every part of the car: bumpers and front panels; dashboard; instrument carriers; consoles; seats; roof elements; floorpans; and the rear fenders. Most of these materials are plastics.
Meanwhile, Renault is on track to incorporate 20% recyclate in its new cars by 2015. The manufacturer’s latest Megane was its first vehicle to be specifically designed for recycling and the current Scenic contains 34kg of recyclate, or 14% of the vehicle’s total. In 2008, Renault also launched a joint venture with Sita France to develop end-of-life (ELV) recycling programmes.
The Bureau of International Recycling (BIR) provides a good summary of the facts about plastics and their recycling which should be compulsory reading for designers, purchasing managers, board executives and works managers. The main points are as follows:
- One tonne of recycled plastic saves 5,774 kWh of energy, 16.3 barrels (2,604 litres) of oil and 22 cubic metres of landfill
- There is an 80-90% reduction in energy consumption in production with recycled plastic compared to production from virgin materials (oil and gas)
- Worldwide trade of recyclable plastics is valued at $5 billion per year and represents a total of 12 million tonnes
Across all industries, the technology and techniques for recycling have advanced massively over the past 20 years and recycled materials have become so commonplace that most consumers are unaware that the products they are using are not completely new.
PPR Wipag, which is based in Dover, UK, has built a reputation for recycling dashboards. “The dashboard is a very complex component – it carries the airbags,” says Jonathon Weston, the company’s managing director. “Such parts have to go through rigorous approval processes. We have developed the ability to separate mixed and multilayer materials, process them and turn them into completely acceptable raw material, ready to be used in the same or similar applications.”
Production scrap and used plastic parts undergo repelletisation and/or compounding, which can be tailored to customer requirements. Plastic composites are separated into single fractions to a high degree of purity, which are then used as regrind or as recyclate. Painted plastics are separated from their coatings by a completely mechanical process and can be reused in visible parts.
During manufacture, a multi-layered instrument panel accumulates around 2kg of multi-layered punch waste. Producing 2,000 pieces a day will thus generate around 4,000kg of waste – including 40-80% thermoplastics. Wipag says that it can reclaim and separate those materials without appreciable impact on their attributes, allowing them to be reused as conventional thermoplastics.
Long-strand glass fibre-reinforced PPs are increasingly being used as carrier material in dashboards. One concern is that reuse of recyclate will result in contraction of the fibre length, but tests at Wipag have suggested that gentle conditioning of long-fibre reinforced materials can actually lead to improved component characteristics in reuse.
Meanwhile, recycling ELV bumpers is complicated because old bumpers are typically made from a mixture of PP and EPDM grades and contain varying talc content, different colours, other plastics, metal, dust and dirt. Wipag has applied a number of separation steps, paint removal, re-compounding and melt-fine filtration to achieve the same properties in PP/EPDM recyclate as current virgin materials. The company has fully automated the process in order to make it economically attractive. Wipag says its de-painting procedure also removes accumulated working life residues. The separation process has been in commercial operation since the mid-1990s and has been applied to different thermoplastic carrier substrates, like PP-talc, PC/ABS, SMA and PPE and PP-LGF.
Dutch company DSM Engineering Plastics, which supplies polyamide (PA) compounds including PA 6, 66 and 4.6, has formed a collaborative partnership with Ravago Group, which specialises in the compounding and recycling of plastic and elastomeric raw materials. The two companies have developed a portfolio of glass-reinforced, recycled PA 6 compounds, which will be offered by DSM directly and distributed by Ravago Group member Resinex. The recycled PA 6 grades, which DSM is marketing under its Akulon brand, contain more than 50% post-consumer resin from dependable sources. DSM is supplying grades with 30% and 35% glass fibre reinforcement and says that they are suitable for under-the-bonnet applications such as air intake manifolds and engine covers.
“Consistency and purity is one of the main challenges with recyclate,” says Joost d’Hooghe, segment sales manager automotive, Europe for DSM Engineering Plastics BV. “When material has been injection-moulded once, its performance is affected. The collection of materials available now is reasonable, but it doesn’t match virgin. We have a single-source supplier to ensure that the material is consistent; if we had a large number of suppliers the quality would vary. Ravago has the experience with post-consumer material and decontamination.”
Dutch company Polyscope, a global provider of styrene maleic anhydride (SMA) copolymers and compounds, is a supporter of internal waste recycling. Its instrument panel compounds include 20% recycled industrial materials and the company claims they retain 99% of their properties. Given that its sunroof mounts, such as those on Citroën’s DS3, are effectively the outside lines of rectangles, the ability to reuse production scrap is going to be an enormous help in reducing material wastage. However, DSM seems to prefer post-consumer to post-industrial recyclate.
“If you want a closed-loop, then you need post-consumer,” d’Hooghe explains. When it comes to the difference in performance between virgin and recycled material, the situation is less distinct. “We have a prime portfolio of products and recycled material’s performance is slightly lower than virgin. A large volume of recyclates is available, but it is not necessarily of the quality needed. It can be used under-hood, for engine covers, for example, and we have also investigated its use for air intakes.” He adds, “Weld line performance can be a challenge and some design aspects need to be taken into account.”
When pressed for a figure to differentiate virgin and recyclate, d’Hooghe prefers not to be specific. “We have data sheets, but I don’t want to offer a single figure. It can be better in some applications – it depends.” Tensile strength can be lower but d’Hooghe agrees that it is over 90%.
As more vehicles reach the end-of-life stage, progressively more used plastic is going to become available. The choice is pretty clear: learn to make greater use of it or face the inevitability of rising costs, as landfill and similar disposal methods become ever more problematic.
